This invention relates to engine cylinder deactivation apparatus and, in particular, to hydraulic lost motion deactivation apparatus incorporating a gas/vapor purge.
It is known in the art of engine cylinder deactivation to provide switchable hydraulic lash adjusters operable to either actuate the valves of a deactivation cylinder or to maintain the valves closed through lost motion features of the hydraulic lash adjusters (HLA). Similar mechanisms may be provided in a hydraulic valve lifter (HVL) which includes internally a hydraulic lash adjusting mechanism and so may be referred to broadly as a hydraulic lash adjuster.
Conventional lash adjusters are supplied with pressurized oil through a lash adjuster gallery or lifter gallery to annular feed grooves or intake ports which provide oil pressure to take up the lash in the valve train between the valve and its associated tappet or other-actuator. Lash adjusters and valve lifters with cylinder deactivation have an additional port for a lock pin which connects through control passages and a control channel with a valved oil pressure supply. A three-way solenoid-actuated hydraulic control valve may be used to connect oil pressure to the lock pin for cylinder deactivation or switching of the lash adjusters in a supply mode of the three-way valve and to exhaust oil pressure from the oil passages and control gallery in an exhaust mode.
Such cylinder deactivation apparatus typically use complex systems of bypass channels and hydraulic bleeds in order to purge air or other gas/vapor from the system to insure consistent response to control signals. This is necessary to provide reliable actuation or deactivation of the switchable hydraulic lash adjusters in the apparatus when the hydraulic control valve is actuated to make a change in operation. These bleed and bypass systems may add considerable complexity to the deactivation apparatus itself. Thus, a simplified system for purging gas/vapor, primarily air, from the hydraulic cylinder deactivation apparatus is desired.
The present invention provides simplified cylinder deactivation apparatus wherein the oil supply passages and control channels utilized for actuating the switchable hydraulic lash adjusters are purged of air with oil flow through restricted bypass means from the pressure oil supply. The control channel or the complete oil passage and control channel system are purged by exhausting the bypass oil flow through a solenoid-actuated hydraulic control valve exhaust port during engine start up and optionally during operation in the non-pressurized mode of the cylinder deactivation apparatus.
In one embodiment, a restricted bypass from the oil pressure supply enters the control channel at a distal end and is exhausted from the control channel through the solenoid valve exhaust port at the other end of the control channel adjacent the control valve. Air or other gas or vapor accumulating in the control channel is thus purged from the system during early stages of the engine operation.
In an alternative embodiment, the pressure oil supply from the lash adjuster gallery to the lash adjuster or valve lifter inlet is connected at each of the switchable lash adjusters with the deactivation port of the respective lifter through a restricted bypass groove in the lifter body. When the deactivation supply pressure is shut off by the hydraulic control valve, pressure oil is fed through the restricted bypass in each lash adjuster body to the gallery passages and control channel of the deactivation apparatus. The oil thus supplied purges the system of air which is exhausted from the system through the open exhaust valve of the three-way hydraulic control valve.
In both cases, when the control valve is actuated to close the exhaust and open the supply line, pressure oil is fed through the control channel and associated passages to the switchable hydraulic lash adjusters at the deactivation ports, thereby switching the lash adjusters to deactivated mode. In this condition, the oil pressure supplied to the deactivation channels and passages balances the pressure supplied to the lash adjuster mechanism itself and thus there is no loss of oil or purge flow through the system. With these arrangements, the purging of air from the control channel and connecting passages is accomplished primarily through the control channel and connecting passages themselves, without the need for additional separate channels and bleed passages that add to the complexity of the system.
In modifications of the two foregoing embodiments, a hydraulic seal is added to the lifter body. An annular channel is provided below the locking pin of each deactivation valve lifter and is supplied with pressurized oil through a vertical channel from the oil gallery. In one case, the annular channel is always below the associated control passage and the oil pressure prevents air from below the lifter gallery from entering the control passage and causing air bubbles that may interfere with the timing of deactivation actuation. In another case, the annular channel is positioned below the control passage on the actuating cam base circle but in alignment with the control passage when the cam raises the lifter to open an engine valve. In the lower position, the seal functions as in the first case above. However, when the lifter is raised cyclically as the cam rotates, oil passes from the oil gallery through the annular channel into the control passage to help flush aerated oil out of the system. Thus, entry of air from below the lifter gallery is prevented and, in the latter case, flushing of air out of the system is aided.